Condensate recirculation system in an adsorption refrigeration machine

ABSTRACT

The invention describes a condensate return device which is arranged between a condenser and an evaporator of an absorption refrigeration machine and which is designed as a pipe which is open to vapor.

The present invention relates to a condensate recirculation device for an adsorption refrigeration machine, comprising at least one pipe, which connects the condenser to the evaporator, designed as a pipe that is open to vapor and preferably has a pressure reducing element. In addition, the invention relates to the use of the condensate recirculation device and a method for recirculation of the condensate.

Refrigeration machines described in the prior art are generally used for heating and/or cooling buildings. Refrigeration machines are based on thermodynamic cycle processes in which heat is taken up at a temperature below ambient temperature and released at a higher temperature, for example. These thermodynamic cycle processes resemble those of a heat pump. Known refrigeration machines in the prior art include, for example, adsorption refrigeration systems, diffusion-absorption refrigeration machines and compression refrigeration systems.

The adsorption refrigeration machine consists of at least one adsorber-desorber unit, an evaporator, a condenser and/or a combined evaporator/condenser unit, which are accommodated in a combined container or in separate containers, which are then interconnected by pipes or the like for the flow of refrigerant. The advantage of sorption machines in comparison with conventional heat pump technology is that adsorption/desorption sequence takes place only through the temperature control of the sorbent. Thus the container of the adsorption machine can be hermetically sealed and airtight. When using water as the refrigerant, for example, the adsorption refrigeration machine preferably operates in the reduced pressure range.

The adsorption which takes place in an adsorption machine is a physical process in which a gaseous refrigerant (water, for example) is adsorbed onto a solid. Desorption of the refrigerant, i.e., the release of the refrigerant from the solid, requires an input of energy. In an adsorption refrigeration machine, the refrigerant (which picks up heat at a low temperature and low pressure and releases heat at a higher temperature and higher pressure) is selected so that a change in the physical condition is associated with adsorption and/or desorption. Substances having a fine porosity and consequently having a very large internal surface area are described as adsorbents in the prior art. Advantageous materials include activated carbon, zeolites, aluminum oxide or silica gel, aluminum phosphates, silica aluminum phosphates, metal silica aluminum phosphates, mesostructure silicates, organometallic structures and/or microporous materials comprising microporous polymers. The adsorption material may advantageously be applied in various ways, i.e., it may comprise a bed, adhesive bonding and/or crystallization. Due to these different forms of application, the adsorption machine may be adapted to different requirements. The machine may thus be adapted to the location or to the refrigerant. Furthermore, the layer thickness of the adsorption material is crucial for the performance of the adsorption material.

In the process of the adsorption machine, the heat of adsorption and the heat of condensation must be removed from the system. This usually takes place by way of a flow of heat transfer medium, which transports the heat to a heat sink, e.g., to a heat exchanger, which releases heat to the ambient air. However, if the heat of adsorption and/or the heat of condensation is/are dissipated poorly or not at all, the temperatures and thus the pressures inside the adsorption machine would increase and the adsorption process would come to a standstill. The efficiency of an adsorption machine can thus be increased substantially by an improved heat transfer, which necessarily also improves the profitability of the system.

A vacuum tank is usually necessary for evaporation in sorption machines because, for example, water may be used as the refrigerant, and consequently, low pressures are required.

DE 34 08 193 A1, for example, describes a method for operating an adsorption refrigeration machine. This method serves to increase the temperature of heat at which the first and second desorbers (adsorbers) are switched periodically between adsorption phase and desorption phase and are operated in opposing phases. A two-step internal heat exchange is performed before switching the modes of operation of the two absorbers. This internal heat exchange initially comprises a pressure equalizing step and a subsequent heat transfer through a heat transfer loop. This process is continued after a thermal equalization has been achieved between the two absorbers. This means that after switching between the adsorption phase and the desorption phase, a temperature equalization between the adsorbers is performed to utilize the heat remaining after the desorption phase.

An adsorption refrigeration machine also has a recirculation unit, which serves to ensure that there is a discharge of a fluid, in particular a refrigerant, between components of the adsorption refrigeration system, while maintaining a pressure difference that fluctuates according to the operating conditions. This ensures a continuous flow of the fluid. The recirculation unit is important in particular for recirculation of the liquefied refrigerant from the condenser into the evaporator because recirculation of a refrigerant in the system is maintained only in this way. In addition, the recirculation unit contributes toward an optimized process efficiency of the system and is therefore an important component. However, it should be noted here that the recirculation unit is designed to save space, and therefore compact adsorption refrigeration machines can be implemented.

Different possibilities which achieve recirculation of condensate are described in the prior art:

-   -   U tube with a corresponding length to permit compensation of the         prevailing pressure differences;     -   Water barrier for vapor from the condenser;

One disadvantage here is that the production of these recirculation units is relatively complex and the height of the adsorption refrigeration machines depends essentially on the length of the condensate recirculation.

Such a recirculation unit is disclosed in DE 38 08 653 C2, for example. The liquid coolant collected in a condenser container and stored at the bottom of the container is sent to the evaporator via a recirculation unit in the form of a pipeline based on a pressure difference.

In addition, DE 10 2008 012 598 describes a recirculation unit for an adsorption refrigeration system, comprising an arrangement of a first siphon (U tube) through which a fluid can flow, a first inside pipe directed downward, a first outside pipe which surrounds the inside pipe and is closed at the bottom and a first pressure compensating pot, which has a first outlet and is arranged at an upper end of the outside pipe. A second siphon is connected downstream at the outlet of the first siphon, having a second inside pipe directed downward, a second outside pipe surrounding the second inside pipe and sealed at the lower end and a second outlet arranged on the second outside pipe. The siphon is high enough to be able to compensate for the fluctuating pressure differences between the evaporator and the condenser by means of a hydrostatic water column. The U tube functions as a vapor barrier because water always remains in it, thereby ensuring that the pressure separation between the condenser and the evaporator is maintained.

One disadvantage of the recirculation units disclosed in the prior art is that they do not have a compact design and they cannot be arranged in a space-saving manner on the adsorption refrigeration machine, so it is also impossible to produce compact adsorption refrigeration machines. To ensure the function of the recirculation units, they must always consist of several units (or siphons) connected in series, which makes the recirculation unit very complex and expensive to install. Furthermore, it has been found that the cascade arrangement of siphons is subject to trouble and is difficult to maintain. In addition, the recirculation units have a plurality of metal pipes, thus greatly increasing the weight and the manufacturing costs of the adsorption machine.

Furthermore, the pressure separation by means of a simple siphon cannot usually be emphasized with adsorption refrigeration machines in low positions, if the available hydrostatic pressure and/or the hydrostatic level is not sufficient in the case of a low apparatus. In complete idling of the condensate recirculation, the vapor can be transported from the condenser and thus can create a significant loss of refrigeration capacity.

The object of the present invention was thus to provide a device which would not have the disadvantages and shortcomings of the prior art and which would allow the production of a compact adsorption refrigeration machine, so that condensate is efficiently directed from the condenser into the evaporator.

This problem is solved by the independent claims. Advantageous embodiments are derived from the dependent claims.

A condensate recirculation device which does not have the disadvantages and shortcomings of the prior art, is thus made available. This device has at least one pipe, such that at least one pipe is connected to a condenser and an evaporator of the adsorption refrigeration machine so that it is open to vapor, and it is preferable for a pressure reducing element to be present in the tube. The device according to the invention has a simple design, has no moving parts and has a long service life and the condensate can flow from the condenser into the evaporator without any backlog. It may be preferable to arrange multiple tubes between the evaporator and the condenser.

The present invention relates in particular to a condensate recirculation device for an adsorption refrigeration machine comprising at least one pipe, such that at least one pipe is connected to a condenser and an evaporator of the adsorption refrigeration machine so that it is open to vapor, and a mass flow of liquid refrigerant and a small mass flow of vaporized refrigerant, preferably less than 0 to 3%, preferably 0.5% to 2%, especially preferably 1% to 1.5% of the mass flow of liquid refrigerant flows through the condensate recirculation device, in particular through the pipe.

The pipe is preferably connected to the evaporator and the condenser in a form-fitting manner or in a physically bonded manner. Form-fitting joints are preferably formed by the engagement of at least two joining partners. The form-fitting connections comprise screws, rivets, pins or clamps. The pipe may preferably be connected to the components of the adsorption refrigeration machine by means of screws or rivets with the corresponding seals.

In addition, the pipe may be mounted on the condenser and the evaporator by means of physically bonding agents. Physically bonded connections are held together by atomic or molecular forces. They are at the same time non-releasable connections, so they can be released only by destruction of the components and/or the joining means. Physically bonded connections comprise soldering, welding or adhesive bonding.

Those skilled in the art will know that form-fitting or physically bonded connections, for example, welded joints, may be embodied in the form of one or more joining points (e.g., welding points) or as a linear joint (e.g., a weld) or a surface connection.

A fluid comprising a gaseous and/or liquid fluid may flow from the condenser through the pipe and into the evaporator by means of the condensate recirculation device according to the invention. In other words, it is preferable for a flowing fluid comprising gaseous and liquid fluid to be present in the pipe. In the sense of the present invention, a fluid refers to a gas or a liquid in particular. The refrigerant, which may be referred to as a fluid in the sense of the present invention, is present as a vapor and as a liquid in the condenser.

The gaseous refrigerant present in the condenser must not enter the evaporator to any significant extent. The condensate recirculation device according to the invention is constructed to be open to vapor, so that a defined mass flow of vapor flows from the condenser through the device into the evaporator. However, the refrigerant flowing in vapor form through the device to the evaporator is adsorbed by the adsorption material of the adsorber/desorber unit, but it does not contribute to the refrigeration capacity of the evaporator because the evaporation of the refrigerant does not take place in the evaporator chamber. The actual refrigeration process is therefore impaired and there is a loss of power. The power loss occurs due to the fact that vapor enters the evaporator directly from the condenser. Due to the condensate recirculation according to the invention, the power loss amounts to less than 2%.

According to the invention, a pipe having a specific diameter and a corresponding length has surprising advantages in comparison with the prior art. The diameter and the length of the pipe are selected so that the condensate can easily flow to the evaporator without any backlog, on the one hand, while on the other hand, the vapor flows from the condenser into the evaporator in an insignificant amount, i.e., a negligible amount.

This effect is created in particular by a drop in pressure in the vapor flow in the tube and is based on the great difference in density between the liquid condensate and the gaseous vapor. As a result of this density difference, the mass flow of vapor through a pipe with a certain diameter is up to 200 times lower in the case of water as the refrigerant than the flow of liquid refrigerant, for example. Those skilled in the art are aware that it is the mass flow and not the volume flow of vapor that forms the critical variable for the loss of refrigeration capacity. In the ongoing adsorption refrigeration process, the mass flow of condensate fluctuates between zero and the maximum value. The condensate recirculation device also ensures that even with complete emptying, the flowing vapor has a very low mass flow, which corresponds to a negligible loss of refrigeration capacity. It is preferable for the mass flow of liquid condensate to be 0.4 g/s per kW refrigeration capacity, wherein the vapor mass flow, in particular the mass flow of the vaporized refrigerant at a standstill, amounts to max. 1% of the mass flow of the liquid condensate. A vapor mass flow of 0.004 g/s per kW refrigeration capacity is preferred. It was completely surprising that an adsorption refrigeration machine could be operated efficiently despite the use of a condensate recirculation device that is open to vapor. It would not be unreasonable for a skilled person to reconstruct the invention and to provide a pipe that will allow the required mass flows of liquid and vapor condensate to pass through. Those skilled in the art can perform simple comparative experiments for this purpose.

In a preferred embodiment, the invention relates to a condensate recirculation device for an adsorption refrigeration machine comprising at least one pipe, such that the pipe is connected to a condenser and to an evaporator of the adsorption refrigeration machine so that it is open to vapor and a mass flow of vaporized refrigerant of max. 0% to 3% preferably 0.5% to 2% and especially preferably 1% to 1.5% of the mass flow of the liquid condensate, in particular refrigerant, flows through the pipe. It was completely surprising that it is possible to create a condensate recirculation device in which the mass flow of the vaporized refrigerant is max. 1% of the mass flow of the liquid refrigerant flows, in addition to the liquid condensate, in particular the liquid refrigerant, such that the decline in power of the adsorption refrigeration machine is less than 4%, preferably less than 2%. This constitutes a departure from the recirculation equipment described in the prior art because the equipment in the prior art is designed to be exclusively closed to vapor and thus not allow a mass flow of vapor to pass through.

The following formulas can preferably be used to calculate the dimensions on the example of a pipe:

Vapor Flow (Loss of Refrigeration Capacity):

The loss of refrigeration capacity due to the vapor flow from the condenser to the evaporator can be calculated using the following formulas:

{dot over (Q)}={dot over (m)}·ΔH

{dot over (Q)}: power

{dot over (m)}: mass flow

ΔH_(v): enthalpy of evaporation of the refrigerant

The following also holds:

{dot over (m)}=ρ·{dot over (V)}

ρ: density (vapor here)

{dot over (V)}: volume flow

{dot over (V)}=u·A

u: velocity of flow

A: cross-sectional area of the line

On the whole:

{dot over (Q)}=ρ·u·A·ΔH _(v)

The velocity of flow can be calculated using the following equation:

${\Delta \; p} = {\left. {\xi \frac{\rho}{2}u^{2}}\rightarrow u \right. = \sqrt{\frac{2\Delta \; p}{\rho \cdot \zeta}}}$

Δp: pressure drop (here the differential pressure between the evaporator and the condenser)

ξ: coefficient of resistance

On the whole:

$\overset{.}{Q} = \sqrt{\frac{{2 \cdot \Delta}\; {p \cdot A^{2} \cdot \rho \cdot \Delta}\; H^{3}}{\zeta}}$

The decline in power is a function of the coefficient of resistance:

$\overset{.}{Q} \sim \frac{A}{\sqrt{\zeta}}$

{dot over (Q)}: power loss

ξ: coefficient of resistance

In the case of a pipe, the following equation holds for the coefficient of resistance:

$\zeta = {\lambda \frac{l}{d}}$

λ: coefficient of friction of the pipe

l: length of the pipe

d: diameter of the pipe

Condensate:

A similar equation also holds for the mass flow of the condensate:

$\overset{.}{m} = \sqrt{\frac{{2 \cdot \Delta}\; {p \cdot \; A^{2} \cdot \rho}}{\zeta}}$ $\overset{.}{m} \sim \frac{A}{\sqrt{\zeta}}$

The optimal selection of geometry and the coefficient of resistance of the condensate recirculation device should ensure that:

-   -   the maximum allowed power loss is not exceeded;     -   the condensate flows from the condenser to the evaporator with         no problem and without any accumulation in the condenser, for         example.

Addition advantages of the invention include:

-   -   smaller and lighter than the previous state of the art     -   independent of the size and/or height of the adsorption machine     -   simple, no moving parts, long service life     -   in contrast with the prior art the condensate recirculation         device does not vibrate during operation of the adsorption         refrigeration machine     -   simpler to manufacture     -   the design of the recirculation is very flexible because only         the length and the diameter of the pipe in particular are         crucial     -   low loss even at a standstill due to the high pressure drops in         the pipe     -   the condensate is guided reliably and without accumulation in         the condenser to the evaporator     -   has a long service life which advantageously corresponds to the         service life of the machine as a whole     -   is not subject to problems     -   simple design, operation without complicated regulation         technology, without actuators or sensors and without components         that can easily become clogged     -   is self-regulating     -   is independent of the size and type of the adsorption         refrigeration machine

In the sense of the present invention, a pipe describes in particular an elongated hollow body whose length is usually significantly greater than its cross section. It may also have a rectangular, oval or other cross section. The pipe preferably has a length of 0 to 2 meters, a length of 0.1 m to 1 m being advantageous in particular. The pipe may simply be connected to the components of the adsorption refrigeration machine and can be adapted easily so that it can be used universally. For example, an installer may shorten the pipe on site and adjust it to a required length. It has also been found that the pipe is very low maintenance of even maintenance-free because it is a simple construction. In the sense of the invention it may also be advantageous to design the pipe to be short so that it is present merely as an opening between the condenser and the evaporator. This may be necessary in the case of very compact systems in particular. It is nevertheless described in the prior art. Accordingly, a pipe in the sense of the invention also includes in particular an opening or a passage through which a mass flow of refrigerant in both liquid and vapor form can flow. Consequently, it may be preferable to arrange at least one opening or passage between the condenser and the evaporator.

The pipe is preferably made of metal, plastic and/or ceramic materials. Preferred variants include steel, stainless steel, cast iron, copper, brass, nickel alloys, titanium alloys, aluminum alloys, plastic, combinations of plastic and metal (composite pipe), combinations of glass and metal (enamel) or ceramic. It may also be preferable to connect several pipes together in a force-locked and/or physically bonded manner. Force locked connections include tension rings, molded parts, bent pipe pieces, screws or rivets. Physically bonded connections include adhesive bonding, welding, soldering or vulcanization. Because of the good thermal conductivity, copper or aluminum is advantageously used as the material for the pipes, but it may also be advantageous to use stainless steel because the latter has high static and dynamic strength values and a high corrosion resistance. Pipes made of plastic, for example, polyvinyl chloride, are especially lightweight and flexible and can thus reduce the weight of the adsorption refrigeration machine. Ceramic materials comprising structural ceramic materials have a high stability and a long service life. Combinations of the materials listed above are especially advantageous because different physical properties can be combined in this way. The preferred materials meet the high technical fabrication demands of a pipe and/or of an adsorption refrigeration machine because they are stable with respect to high temperatures or varying pressures.

It is preferable for the pipe to have a diameter of 0.01 to 15 mm, preferably 2 to 10 mm and especially preferably 3 to 6 mm. In a preferred embodiment of the invention, the pipe is designed to be angled or not straight. It may also have bends or angles. It is preferable for the pipe for a 10 kW adsorption refrigeration machine to have a diameter of 4 mm and a length of 2 mm, such that the refrigeration capacity loss amounts to 1.5% in particular. The diameter/length ratio is preferably 1 to 500, and the ratio of the power of the adsorption refrigeration machine is given only as an example.

There is preferably a pressure reducing element inside the pipe. However, it may also be preferable for the pipe to function as a pressure reducing element because of its ratio of diameter to length. This means that the diameter is reduced or the length is increased to the extent that the liquid condensate (in particular the refrigerant) and a small volume of vapor refrigerant, preferably less than or equal to 1% of the mass flow of the liquid condensate flows out of the evaporator and through the pipe into the evaporator. The power loss by the adsorption refrigeration machine is preferably less than 2%. Those skilled in the art are aware that the diameter of a pipe can be reduced to the extent that only a liquid flows through it and there is little or no vapor. In the sense of the present invention, this state may be referred to as being open to vapor.

The pressure reducing element which is preferably arranged in the pipe is preferably a throttle, a valve or a cutoff valve. The elements may be integrated into a pipe and cause a local constriction of the flow cross section. Different valves, which may be divided according to their geometric shape, may advantageously be integrated into the pipes. Valve used here may include straight-way valves, angle valves, Y-type valves with an inclined seat and/or three-way valves. The flow rates in the pipelines can be controlled accurately and precisely by varying the nominal width in the use of the valves, and the pipeline can be sealed reliably with respect to the environment. The valves may advantageously be operated by hand, by medium, by machine or electromagnetically. A throttle in the sense of the present invention is preferably a conical piece of pipe inside a pipe, where concentric or eccentric reductions are also preferred.

In another preferred embodiment, the pressure reducing element is an aperture and/or a built-in part. A built-in part, for example, comprises a reduced cross section of a pipe installation or parts of the pipe installation of a section, a T-piece having a reduced outlet or a sleeve, an aperture, a fitting or a measurement and control system with a reduced cross section. Those skilled in the art of hydrodynamics will know that such a built-in part can be integrated into a pipe. The pressure reducing or cross section reducing element may advantageously be integrated into one or more pipes, such that it may be advantageous to design them to be adjustable and variable. This means that the pressure reducing elements may be regulable or self-regulating, so that the optimal or preferred pressure reduction can preferably be achieved at any time and under any boundary conditions because the cross section of the pipes through which the flow passes can be increased or decreased.

The adjustability of the pressure reducing element may be implemented manually, for example, by means of a hand valve. However, it may also be preferable for the pressure reducing element and the pipe cross section through which the flow passes to be adjusted automatically and/or in a self-regulating fashion. The pressure reducing element may be equipped with measurement and control devices which measure the pressure in the pipe, for example, and then vary the nominal width of the pipe, i.e., the cross section of the pipe by means of the pressure reducing element based on the results of these measurements.

It may thus be preferable for the pressure reducing element to alter the nominal width of the pipe or pipes, i.e., the cross section of free flow through the pipes, such that essentially liquid condensate and a small volume of vapor will flow out of the condenser and into the evaporator.

In another preferred embodiment, at least one measuring and/or regulating device is installed on the condensate recirculation device, in particular the condenser and/or the evaporator. The measuring and/or regulating device measure the physical properties of the refrigerant in particular, including the temperature and/or pressure. The measuring and/or regulating device may thus determine the vapor pressure in the condenser, such that the measured variables are digitized and output as data. It is advantageously also possible to save the measured data and to use this data for comparison purposes, thus permitting optimization of the adsorption refrigeration machine. It may be preferable for the measured data—the so-called actual value—to be compared with given setpoint values, and then any resulting difference may lead to the regulating device preferably causing a variation in the nominal width of the pipe and/or the cross section of the free flow through the pressure reducing element. In this way, the condensate recirculation device can be adjusted easily and quickly to different modes of operation or different operating points of the adsorption refrigeration machine. The setpoint values here preferably correspond to values which define a certain mode of operation.

Those skilled in the art will know that operating points may denote certain points in the characteristics map or on the characteristic line of a technical device, preferably a sorption machine, especially preferably an adsorption refrigeration machine or an adsorption heat machine, which may be implemented on the basis of the system properties as well as external influences and parameters that act on the system. Examples include the temperatures of the heat sinks and sources or the total volume flows in the recirculation in the evaporator or the desorber strand.

In the sense of the present invention, the system configuration preferably denotes the configuration of the machine, i.e., for example, the internal hydraulic wiring of the components of the machine, the internal wiring of the components on the refrigerant side or the altered basic design of the machine (e.g., the number of adsorbers, operation of the evaporator, of the condenser, etc.).

The condensate recirculation device can be connected easily to the condenser and to the evaporator by means of fastening devices with which those skilled in the art are familiar, so that a connection that is open to vapor exists between condenser and condenser. It was completely surprising that a pipe could be used for this purpose that causes a reduction in pressure either because of the combination of the diameter and length or by means of a component such as an aperture. This surprising achieves the result that the liquid condensate can flow out of the condenser and into the evaporator, such that vapor refrigerant also flows into the evaporator. However, the flow rate of the vapor is so low that only a reduction in the power of less than 2% occurs. The mass flow of vapor in particular advantageously amounts to max. 1% of the mass flow of the liquid refrigerant. This is a departure what is customary in the industry and opens up a novel technical field because when using this pipe, it is no longer necessary to adjust the equipment to different modes of operation of a sorption machine, preferably an adsorption machine. This in turn leads to a reduction in the manufacturing costs and to universal usability of the machines. Furthermore, the condensate recirculation device is a simple design which can be implemented in various lengths or dimensions. The use of recirculation devices which are open to vapor is avoided in the prior art, so that the present invention departs from what is conventional in the industry.

The condensate recirculation device may advantageously be used with two adsorbers, for example, in the case of single-chamber systems, but also may be used with only one adsorber of an adsorption refrigeration machine even for dual chamber of multichamber systems. Furthermore, it can be adapted easily and quickly to other types of sorption machines. The machines need not be altered fundamentally with regard to the equipment to do so.

Those skilled in the art will be aware of the fact that the pressure drop refers to the pressure difference resulting from friction on the wall and internal fluid friction in the pipelines. Different pressures preferably prevail in the condenser and in the evaporator. This achieves the result that essentially no liquid or vapor refrigerant flows out of the evaporator and into the condenser. Inclusion of the term “essentially” is an unclear formulation for those skilled in the art from the standpoint of pressure because those skilled in the art would recognize on the basis of the overall disclosure of the teaching according to the invention that the pressure is preferably different in the two components of the adsorption refrigeration machine and this wording of course includes both small and great pressure differences equally. The different pressures can be determined, for example, by measurement methods described in the prior art.

The average person skilled in the art will have assumed so far that no vapor can flow through the recirculation devices out of the condenser and into the evaporator because this would result in a power loss by the adsorption refrigeration machine. In other words, recirculation devices that are open to vapor were not used for the stated purpose in the past because the technical world had assumed that this would be associated with a decline in power. However, it has been found that even the use of at least one pipe that is open to vapor as a condensate recirculation device, in particular in use in an adsorption refrigeration machine, does not lead to a substantial loss of power or other disadvantages. This was completely surprising and constitutes a departure from the prior art. It is preferable here for the mass flow of vapor in particular the vapor refrigerant to amount to in particular max. 1% of the mass flow of the liquid refrigerant. Those skilled in the art can reconstruct the present invention with the help of this information without having to make a contribution according to the invention because they can determine the dimensions of the condensate recirculation device, in particular of the pipe, by simple comparative tests without requiring any great technical effort.

The present invention also relates to an adsorption refrigeration machine comprising a condensate recirculation device, comprising at least adsorber/desorber unit, one condenser and evaporator unit, wherein the condensate recirculation device consists of a pipe that is open to vapor between the evaporator unit and the condenser unit and there is a pressure reducing element in the pipe. It may also be preferable to provide at least one pipe, preferably several pipes between the evaporator and the condenser. In addition, the invention relates in particular to an adsorption refrigeration machine comprising at least one adsorber-desorber unit having a heat exchanger and sorption material, at least one condenser, at least one condenser-heat exchanger, at least one evaporator-condenser unit and/or one evaporator-heat exchanger, such that the condensate recirculation device consists of at least one pipe that is open to vapor between the evaporator and the condenser and a pressure reducing element is present in at least one pipe, such that the adsorption refrigeration machine has connection elements and a pipe bushing for hydraulic connection and operation. The average person skilled in the art will know which of the components mentioned above must be used, depending on the type of adsorption refrigeration machine. The list enumerated above is a group of modules, individual units of which may be joined together, depending on the type of adsorption refrigeration machine. The choice of individual components and how they are joined together will be familiar to those skilled in the art.

The present invention also relates to the use of a condensate recirculation device for recirculation of a fluid from a condenser into an evaporator of an adsorption refrigeration machine. In an especially preferred embodiment of the present invention, it is provided that at least one pipe is arranged between the evaporator and the condenser, such that at least one pipe is open to vapor and preferably a pressure reducing element is present in at least one pipe. It is also preferable for at least one pipe to be designed only as a passage or opening and according at least one passage or at least one opening is provided between the evaporator and the condenser.

Furthermore, the present invention relates to a method for condensate recirculation in an adsorption refrigeration machine, comprising at least one pipe which is arranged between a condenser and an evaporator of the adsorption refrigeration machine, such that there is a flow of a liquid refrigerant present in the condenser and a vapor refrigerant through at least one pipe into the evaporator and there is a power drop of less than 5%, preferably less than 2%, by the adsorption refrigeration machine. Preferably at least one pipe has a pressure reducing element.

The present invention will be explained as an example below on the basis of figures although it is not limited to these figures, in which

FIG. 1 shows an adsorption refrigeration machine according to the prior art;

FIGS. 2 and 3 show preferred embodiments of the condensate recirculation device;

FIG. 4 shows an adsorption refrigeration machine, preferably compact, having an alternative design;

FIG. 5 shows a preferred design range of the condensate recirculation device.

FIG. 1 shows an adsorption refrigeration machine according to the prior art. An adsorption refrigeration machine 1 is subdivided into two areas of different pressures, like any conventional refrigeration machine. The condenser 2 and the desorber 3 belong to the high pressure area, while the evaporator 4 and the adsorber 3 belong to the low pressure area. In the recirculation process of the adsorption machine, the condensate must be carried from the condenser 2 (high pressure) back to the evaporator 4 (low pressure). The individual components are interconnected via vapor openings, which allow the vapor to flow.

FIGS. 2 and 3 show preferred embodiments of the condensate recirculation device. The condenser 2 of an adsorption refrigeration machine has a certain filling level of liquid refrigerant 6, which flows out of the condenser 2 and into the evaporator 4 by means of the condensate recirculation device 7. The connection between the condenser 2 and the evaporator 4 is established by at least one pipe, which advantageously contains a pressure reducing element 9. The condensate recirculation device 7 offers surprising advantages in comparison with the prior art due to its specific diameter and the corresponding length of the pipe 8. The diameter and the length of the pipe 8 are preferably selected so that the liquid refrigerant 6 can flow easily, without any problem and without any accumulation, to the evaporator 4, where the vapor from the condenser 2 flows into the evaporator 4 in an insignificant or negligible amount, preferably less than 1% of the mass flow of the liquid refrigerant. This effect is preferably created by pressure drops in the vapor flow in the pipe 8 and is based on the great difference in density between the liquid condensate and the gaseous vapor. The pipe 8 itself may have a pressure reducing element in that an aperture, for example, is arranged in the pipe 8. However, it may be preferable for the diameter and the length of the pipe 8 to be selected so that liquid refrigerant flows through it, but vapor refrigerant has only a low mass flow. In the sense of the present invention, the pipe 8 may also be referred to as a pressure reducing element 9.

FIG. 4 shows an alternative design of an adsorption refrigeration machine in which the condenser 2 is arranged directly above the evaporator 4. The condensate recirculation device 7 is arranged between the condenser 2 and the evaporator 4 with the pipe 8 of the condensate recirculation device 7 being designed as an opening or a passage 8. However, it may also be preferable to arrange at least one, preferably multiple openings and/or passages 8 between the evaporator 4 and the condenser 2. Condensate recirculation then takes place through one or more openings/passages 8, which in the sense of the present invention may be referred to as holes in the partition between the two chambers in particular.

FIG. 5 shows the preferred design range of the condensate recirculation device. A pressure drop is preferred for optimal design of the condensate recirculation device, in particular a diameter/length ratio at which the liquid condensate, in particular the liquid refrigerant, flows through the condensate recirculation device but vapor also flows through it, is preferred. This results in a great loss of performance. On the other hand, a condensate recirculation device may be designed so that the loss of performance is minimal and no vapor flows through it, but the liquid condensate builds up there. It was completely surprising that it would be possible to create a condensate recirculation device which would have a mass flow of liquid refrigerant, in particular condensate, but also in particular max. 1% of the mass flow of liquid condensate, as a refrigerant vapor. This constitutes a departure from that which is customary in the industry.

LIST OF REFERENCE NUMERALS

1 Adsorption refrigeration machine

2 Condenser unit

3 Adsorber-desorber unit

4 Evaporator unit

5 Vapor openings

6 Liquid refrigerant

7 Condensate recirculation device

8 Pipe/opening/passage

9 Pressure reducing element 

1. A condensate recirculation device for an adsorption refrigeration machine, comprising at least one pipe, wherein at least one pipe is connected to a condenser and an evaporator of the adsorption refrigeration machine so that the pipe is open to vapor and no vapor barrier is positioned in the pipe.
 2. The condensate recirculation device according to claim 1, wherein the pipe has a diameter of 0.01-15 mm.
 3. The condensate recirculation device according to claim 1, wherein the resistance coefficient of the pipe is calculated by the equation ξ=λl/d, and wherein the resistance coefficient is selected so that a loss of refrigeration capacity, as calculated by the equation Q=√{square root over (2·Δp·A²·ρ·ΔH²/ξ)}, is less than 5% of the total refrigeration capacity.
 4. The condensate recirculation device according to claim 1, wherein a flowing fluid comprising vapor and liquid fluid is present in the pipe. 5-14. (canceled)
 15. A method for condensate recirculation in an adsorption refrigeration machine comprising: at least one pipe, which is arranged between a condenser and an evaporator of the adsorption refrigeration machine, wherein a liquid refrigerant which is present in the evaporator and a refrigerant vapor flow through at least one pipe into the evaporator, and a power drop of the adsorption refrigeration machine of less than 5% is established.
 16. The method of claim 15, wherein the power drop that is established is less than 2%.
 17. A method for condensate recirculation in an adsorption refrigeration machine comprising: at least one pipe between a condenser and an evaporator, wherein the pipe is open to vapor and has a resistance coefficient that allows a condensed refrigerant to flow from the condenser into the evaporator without an accumulation in the condenser, wherein the flowing steam has a very low defined mass flow, and wherein the loss of refrigeration capacity resulting from the vapor flow is limited to max. 5% of the nominal refrigeration capacity.
 18. The method of claim 17, wherein the loss of refrigeration capacity resulting from the vapor flow is limited to max. 2% of the nominal refrigeration capacity.
 19. The condensate recirculation device according to claim 2, wherein the pipe has a diameter of 2-10 mm.
 20. The condensate recirculation device according to claim 19, wherein the pipe has a diameter of 3-6 mm.
 21. The condensate recirculation device according to claim 3, wherein the loss of refrigeration capacity is less than 2% of the total refrigeration capacity. 